Image reproducing apparatus



July 18, 1944. w. H. BLISS IMAGE REPRODUCING APPARATUS Filed Def. 2. 1941 INVENTOR 7150712101273 5" BY #4 Z AI'TORNEY Patented July 18, 1944 macs: anrnonncmc arrsnarus Warren H. Bliss, Orono, Maine, assignor to Radio Corporation of America, a corporation of Dela- Application mm- 2, 1941, Serial No. 413,285

(Cl. PIS-6.6)

11 Claims.

The present invention relates to picture or image reproducing systems in general and is particularly applicable to facsimile systems wherein the picture signals are transmitted over radio channels. In some instances such transmissions, where occurring over relatively long distances particularly, are not entirely satisfactory due to unavoidable omissions of certain portions of the signals due, for example, to fading and the like.

The present invention has, therefore,'as one of.-

its principal objects that of providing a simple and conveniently used arrangement whereby many of the drop-outs or fill-ins occurring due to fading, static and the like are prevented. In this way, while the correction is in some respects of only a partial nature and does not entirely overcome all of the losses, there nevertheless is produced a better picture record or reproduction for the locker or user.

Broadly speaking, the present invention provides a system wherein for each scanning line of the picture, or any selected portion thereof, there is substituted for any drop-out or fill-in a reproduction of the preceding scanning line or a corresponding portion thereof. To accomplish this result the received signals are preferably caused to' produce a pictorial record in substantially the tureimage and facsimile reception wherein im-. 'proved types of records are produced.

Other objects are to provide a system for receiving facsimile messages wherein the objection to static, fading and the like as influencing the a received signals is made less. apparent in th finished record.

Other objects and advantages, as it will be apperent, will at once suggest themselves to those skilledin the art when the following specification is read in conjunction with the accompanying drawing, wherein the single figure thereof represents schematically one of a plurality of forms which the invention may assume.

In any form of picture transmitting or facsimile apparatus picture signals are transmitted from a sending pointjover a suitable commum .cation channel so that values of light and usual manner, except that at time periods when the received signal strength falls below a predetermined average value the pictorial record will not be produced in the normal manner. However, with the invention, simultaneously with the production of the pictorial record provision is made for producing a non-pictorial record, which may be of several forms, such as a magnetic .record or a record in the form of a latent image and somewhat resembling the sound recordings on a motion picturefllm but having no specific direct reference or likeness to the particular pictorial indication intended. After a predetermined time delay, as hereinafter to be eiiplained in more detail, the non-pictorial record is converted into electrical energy. Then, by means of a switching arrangement activated under the control of the received signals the instrumentality to produce the pictorial record is controlled either directly by the received signals, after, of course, suitable amplification, or the means to produce the pictorial record is controlled by the signals resulting from the conversion of the non-pictorial'record into electrical energy to the exclusion of a direct control from the'signals instantaneously received.

It thus becomes an object and advantage of the present invention to provide a system of picand by the Shore and Whitaker Patent No.

shadow are portrayed as a sequence of signals for each line of the picture and each existing line of the picture is usually followed by a synchronizing signal, although this is not in some instances necessary. After signals representing a complete picture made up of any predetermined number of individual scanning lines have been transmitted these groups of signals are usually followed by a framing signal.

The transmission may be in accordance wit many various forms, among which are the socalled constant frequency variable dot methods, as exemplified, for instance, .by Alexanderson Reissue Patent No. Re. 20,153, of November 3, 1936,

2,083,245, of June 8, 1937, and further explained in Proceedings of the Institute of Radio Engineers, vol. 23, No. 12, for December, 1935, in an article entitled Photoradio apparatus and operating technique improvements," by Callahan et a1. Another method which has been successfully used is the so-called sub-carrier frequency modulation system, as was explained particularly by Messrs Mathes et al; in RCA Review" for October, 1939, in an article entitled "Radio fa'csimile by sub-carrier frequency modulation. Generally speaking, the signals representing the varying light values and the synchronizing or control signals are transmitted to receiving points as modulations of a carrier frequency and such modulations may be amplitude, frequency and/or phase or a mixture of the above. In any such types of systems the transmitted signals representing the lightsand-shadows on the picture accompanied by the synchronizing signals are suitably received, amplified and detected, and then caused to control the operation of a recording stylus or an equivalent instrument. The recording instrument is adapted to produce marking indicia upon a record sheet passed about a recording drum, which is usually rotated or in some instances reciprocated so that one rotation or one motion laterally represents one scanning line. The recording drum is driven from any suitable prime mover, such as a motor, which is maintained at a speed synchronous with the transmitter. Synchronism is usually maintained under the control of the received synchronizing and framing signals.

In the present invention the transmitted picture and synchronizing signals are duly received on a receiving antenna l, or the signals may be received over a suitable wire line communication channel. After the signals received are duly amplified and detected in the receiver and amplifier unit 3, which is of a conventional design, they are then supplied to a line amplifier and converter unit 5, whose output is supplied in parallel to a switching instrument, represented within the dotted outline I, to a switch control unit 9. represented within the dotted outline, and to a magnetic recorder II, which is of any suitable and known type. The signal output from the switching device I is supplied to'a facsimile rethe transformer 35 to an amplifier tube 31 and there amplified. still further, and the output of this amplifier is then coupled through a transformer and a line 40, 4| to actuate the facsimile recorder l5. Simultaneously the output signal from the line amplifier and converter 5 is supplied to a rectifier and filter unit 43 of any conventional design which is a part of the switch control unit 9.

- The time constant of this filter is preferably long corder unit I 5 which is conventionally represented and which is 'driven from any suitable form of primemover such, for example, as the motor I I. The signals from the line amplifier and converter unit 5 are also applied to the switch control unit, which, in the manner hereinafter to be explained, is coordinated with the switching device I. At the same time the signals amplified by the line amplifier 5 are caused to actuate the magnetic recorder unit II and to produc anonpictorial record of the received signals upon a magnetic tape element IS. The tape element I9 is driven over a pair of rollers 2| and 23 which, in turn, are driven from the same prime mover J1 which drives the facsimile recorder l5. Such drive may be in any conventional form, of which the belt drive 25 is illustrated by way of example.

Spaced from the magnetic recorder unit I l, whose output appears at the points 28 and 21, is a magnetic pick-up unit 29 which translates at the points "and M the signals recorded upon the tape I! to convert these signals to electrical energy and then supplies the resultant electrical signals to the amplifier 33. The points 26 and 21,

on the one hand, and 39 and 3|, on the other hand, are spaced apart a distance such that in one preferred form of the arrangement the magnetic tape l9 moves in the direction of the arrow exactly the distance between the points 26 and 21 and the points 30 and 3| during the time that one line of the picture is being recorded by the facsimile recorder I5, and a suitable speed control is established between the motor l1 and the driven elements to achieve the result. The switch control unit 9 is one which is controlled by the available incoming signal, as supplied from the line amplifier and converter 5, in such manner that whenever any drop-outs or fill-ins occur the facsimile recorder is switched to the output of the amplifier 93 for recording purposes instead of to the output of the line amplifier and converter unit 5.

In the particular improvement in which the invention has been illustrated the switching device l and the switch control unit 9 have been shown in further detail. Under normal conditions the incoming signals as passed from the line amplifier and converter unit 5 are passed through enough to hold the output voltage produced across the load resistors and 41 reasonably free from fluctuation due to the dot or impulse frequency of the picture signals. The polarity and characteristics of the rectifier and filter load resistors 45 and 41 are such that the tube 49 is normally in a state of conduction and the tube BI is operating near the cut-ofl point. Under this condition the current flowing'through the load resistor 53 is such that the tube 31 is biased for normal amplifying action and current through the resistor 55 is so low that the battery 51 is sufficient to bias the tube 59 to a cut-ofi. However, when- I ever the incoming signal fails or drops below a predetermined amplitude level due to fading, for

example, the voltage developed across the resisout due to applied bias from the source 58. However, the amplifier tube 59 will now become operative due to the voltage developed across the resistor "55, which shifts the bias of the tubev 59 to a normal value. During the interval of time when the tube 59 is operated the signals from the amplifier 53 will be passed on to the recorder l5 instead of the regular or direct signals from the line amplifier 5. Hence the signals obtained from the magnetic tapel9 by way of the magnetic 5 pick-up unit 29 picking the signals up from the tape at the points 30 and 3| to convert them back into electrical energy so that it may be recorded, as hereinabove explained. As soon as the incoming signal in the receiver amplifier 3, for instance, returns to a normal amplitude it is obvious from what is herein explained that the tube 49 of the switch control unit will again regain control and the recording of the message by the recorder unit l5 will continue in the normal manner. It should be understood that the driving motor I I which is controlled by the received synchronizing and framing signals hereinabove explained is so arranged as to drive both the facsimil recorder and the magnetic tape.

The signals recorded upon the magnetic tape l9. by means of the magnetic recorder H to form the non-pictorial record are then wiped or erased from the tape by the magnetic eraser unit 6| between the points 63 and 64 of which the tape passes. This unit is of standard form and is so well known that further and complete illustration is considered to be unnecessary. After the magnetic record is removed from the tape IS the tape is used again to record signals as before explained.

Many modifications of the system hereinabove suggested will, of course, become apparent and at once suggest themselves to those skilled in the art and, therefore, I believe myself to be entitled to make and us any and all these modifications switching the control of the pictorial reproduc 2,358,681 which fall within the scope of the hereinafter appended claims.

Having now described my invention, I claim: I 1. A picture reproducing apparatus comprising means to receive picture signals, means to pro- 5 and integrating means to, control the time period duce a pictorial record of the received signals and means to produce a non-pictorial record of the received signals, and means for converting the non-pictorial recordinto a pictorial record at falls below a predetermined average value neces-, sary to produce the pictorial record.

2. A picture reproducing apparatus comprising means to receive picture signals, means to produce a-pictorial record of the received signals, 15

time periods when thesignal strength received 10 tion of the received signals to the electrical energy developed by conversion of the magnetic record at time periods when the average signal strength is below a predetermined value so that there is recordeda continuous pictorial record of signals,

within which said switching means is operative. 7. A pictu're'reproducing apparatus comprising means for receiving imag and synchronizing signals, picture reproducing apparatus for converting received signal energy into a-pictorial record, switching means interposed between the picturereproducing means and the-receiving means.

the conversion of the non-pictorial record into a 20 pictorial record to time periods when the average received signal strengthis less than a predetermined value. 1

3. A picture reproducing apparatus comprismeans for producing a non-pictorial record of all receivedsignals, means for converting the nonpiotorial record into electrical energy with a predetermined time delay after the production of the non-pictorial record, switch control, means operative in accordance with the average strength of received signals for controlling the activation of the pictorial reproducer by one of the directly received signals and the signals resulting from conversion of the non-pictorial record into elee-- trical energy, and means for coordinating the rate ing means to receive picture signals, means to as produce both a pictorial record and a non pic torial record or the received signals, means to convert the non-pictorial record into electrical signal. energy subsequent to its, production, and

switching means operative in accordance with'a so departure in incoming signal energy level from a k predetermined average level to select between the two forms of signal energy to control the recording so that the pictorial record is produced at.

t me periods when the signal strength received as instantaneously falls below the predetermined average value under the control of the previously recorded signal energy.

. i. it. picture reproducing apparatus comprising means to receive picture signals, means to produce a pictorial record of the received signals, means to simultaneously produce a non-pictorial record of the received signals, means for converting the ncn-pictorial record into a pictorial record of received signals, and switch-- ing means for limiting the useful conversion or the ncn-pictorial image into a pictorial record'to 4 time periods when the average received signal strength is less than a predetermined value.

5. In a picture receiving apparatus, means for 5 amplifying the received signals, means for recording a pictorial record of thereeeived signals under the control oi. the signals received, means for producing a magnetic record of all of the received signals, means for converting the mag- 5 netic record of the received signals into electrical energy with a predetermined time delay subsequent to the production of the magnetic record. and means for switching the control ofthe pietorial reproduction of the received signals to the electrical energy developed by conversion oi the magnetic record at tim periods when the average signal strength is below a predetermined value so that there is recorded a continuous pictorial 7 record oi signals.

6;. In a picture receiving apparatus, means for receiving picture signals, means for recording a pictorial. record of the received signals, means for producing a magnetic record of all of the received signals simultaneouslywith the pictorial reccrding thereof, means for converting the magnetic record of the received signals into electrical energy a predetermined time subsequent to the production of th magnetic record, means for non-pictorial record, switch control means operative in accordance with the average strength of received signals for switching the control of the reproducing apparatus between the directly received signals and the signals resulting from conversion of the non-pictorial record into electrical energy, and means for normally excluding the ncn-pictorial record element from the control of the pictorial reproductions.

9. A picture reproducing apparatus c0mprisling means for receiving image signals representing a picture subject, picture reproducing apparatus for converting received signal energy into a pictorial record,switching means interposed between the picture reproducing apparatus and the receiving means, means for producing a non-pictorial record of all received signals. means for converting the non-pictorial record into electrical energy a predetermined time subsequent to the production of the non-pictorial record, switch control means operative in accordance with the for simultaneously converting said signals into a non-pictorial record, means for converting the non-pictorial record into electrical signal energy subsequent to the production of the non-pictorial record,- means for intermingling the signals resulting from the conversion of the non-pictorial record into electrical signalenergy with the ini-- tially received signals to produce the pictorial rec-.

0rd, and means for excluding the electrical signal 4 energy developed from the non-pictorial record from the control of the picture reproduction during all time periods when the initially received a recording, the signals received as a pictorial record, means for simultaneously recording the signals received as a non-pictorial electro-magnetic record, means for converting the non-pictorial eiectro-magnetic record of the received signals into electrical energy at predetermined times sub-' sequent to the initial production of the nonpictorial record, means for switching the control 01. the pictorial signal reproduction hetween the initially received signal energy and th electrical energy developed from the conversion of the nonpici'orial' electro-magnetic record, and means for limiting the useful switching period of the pictorial reproduction by the electrical energy developed from the non-pictorial electro-magnetic record to time periods when the average strength of the received signal energy is less determined average intensity.

. WARREN rr. Buss.

thanapre 

